Aspiration Pneumonia: Epidemiology, Pathogens, Risk Factors, Diagnosis and Prevention

This type of pneumonia results from the inhalation of stomach contents or secretions from the oropharynx, which causes an infection of the lower respiratory tract.

In many healthy adults, very small amounts of aspiration occur frequently, but the normal defense mechanisms (cough, lung cilia) eliminate the material without harmful effects.

Aspiration is a common event even in healthy individuals and usually resolves without detectable sequelae.

Markers placed in the stomach can often be detected in the lungs of healthy people using scintigraphic methods.

However, aspiration can cause:

Chemical pneumonitis: chemical irritation of the lungs, which may progress to acute respiratory distress syndrome and / or bacterial infection.

Acute aspiration of gastric contents into the lungs can produce an extremely serious and sometimes fatal disease. This has been called Mendelson syndrome and can be particularly complicated during pregnancy in women.

Obstruction: large volumes of aspirated material can cause obstruction of the respiratory tract.

Bacterial infection: infection of the lower respiratory tract can lead to empyema, lung abscess, acute respiratory failure and acute lung injury.

Pneumonia due to persistent aspiration is often due to anaerobic bacteria and may progress to pulmonary abscesses or even bronchiectasis.

The usual site for aspiration pneumonia is the apical and posterior segment of the lower lobe of the right lung. If the patient is in the supine position, the aspirated material can also enter the posterior segment of the upper lobes.

Epidemiology

It is a common disease. A study of elderly patients involved aspiration pneumonia in 10% or cases of acquired pneumonia in the community studied.

Aspiration pneumonia is relatively common in hospitals and usually involves infection with multiple bacteria, including anaerobes. It is more common in men, small children and the elderly.

Pathogens

The pathogens of acquired aspiration pneumonia are often the normal flora of the oropharynx, including:

  • Stenococcus pneumonia.
  • Staphylococcus aureus.
  • Haemophilus influenzae.
  • Anaerobes – for example, Peptostreptococcus, Fusobacterium and Prevotella spp.
  • Group “Streptococcus milleri”.
  • Klebsiella pneumoniae – increasingly seen in those with a history of alcohol abuse.

Pathogens of nosocomial aspiration pneumonia include:

  • Oral anaerobes – noted above.
  • Cocos Gram-positivos, por ejemplo, Peptostreptococcus spp., Peptococcus spp.
  • Gram-negative bacilli – for example, enterobacteria (Klebsiella pneumoniae, Escherichia coli, Enterobacter spp.), Pseudomonas aeruginosa.
  • aureus resistant to methicillin (MRSA).

Risk factors for aspiration pneumonia

In the absence of a tracheoesophageal fistula, significant aspiration usually occurs only during periods of deterioration of consciousness, with reflux esophagitis with esophageal stenosis or bulbar palsy.

Independent risk factors for aspiration pneumonia are considered:

Impaired consciousness: drug or alcohol abuse, general anesthesia, seizures, sedation, acute stroke, central nervous system injuries, head injury.

Deficient or null mobility due to oral status, increased age, chronic obstructive pulmonary disease (COPD), male sex and increased use of medications.

Swallowing disorders: esophageal stenosis, dysphagia, cerebrovascular accident, bulbar palsy, pharyngeal disease (eg, malignancy), neuromuscular disorders (eg, multiple sclerosis).

Other: tracheoesophageal fistula, ventilator-associated pneumonia for assisted breathing, periodontal disease, gastroesophageal reflux, post-gastrectomy, tracheotomy.

Nasogastric tube feeding is considered less risky than it used to be, due to modern nursing techniques (for example, avoid feeding patients in the supine position).

Presentation

Non-specific symptoms – for example, fever, headache, nausea, vomiting, anorexia, myalgia, weight loss.

  • Tos.
  • Dyspnoea.
  • Pleuritic pain in the chest.
  • Purulent sputum

Signs may include tachycardia, tachypnea, decreased breath sounds and opacity to percussion in areas of consolidation, friction, pleural friction.

A serious infection can lead to hypoxia and septic shock.

Differential diagnosis

Other causes of respiratory distress include:

  • Other causes of pneumonia
  • Bronchiolitis
  • Epiglotitis.
  • Foreign body in the respiratory tract.
  • Asthma.
  • Cardiovascular disease

Investigations for its detection:

  • Blood count: neutrophil leukocytosis.
  • Electrolytes and renal function: dehydration, electrolyte imbalance.
  • Blood culture
  • Blood gases.

Sputum culture:

In patients with bacterial aspiration pneumonia, this may show organisms that usually reside in the pharynx.

X rays

Right, middle and lower lung lobes are the most common sites.

Upright aspiration can cause bilateral lower pulmonary infiltrates.

The right upper lobe often shows consolidation in those with a history of alcohol abuse who aspire in the prone position.

The CT lung is only very occasionally necessary.

Samples obtained from bronchoscopy can help guide the choice of antibiotic treatment.

Administration

Mechanical obstruction: removal of the object, usually by bronchoscopy.

Tracheal suction if seen early.

An intubation with positive pressure ventilation may be necessary.

Bacterial infection of the lower respiratory tract (the choice of antibiotics will be influenced by any recent previous antibiotic treatment, the results of the microbiology culture and the patient’s condition):

Initial empirical antibiotic therapy awaiting culture results.

Antimicrobial therapy should be based on the characteristics of the patient, where the aspiration occurred, the severity of pneumonia, and available information on local pathogens and resistance patterns.

Acquired aspiration pneumonia is often initially treated with co-amoxiclav. It is possible that metronidazole should be added if there is evidence of complications – for example, pulmonary abscesses.

The aspiration pneumonia acquired in the hospital: an adequate combination in patients who have already been recently treated with antibiotics is piperacillin with tazobactam.

The role of steroids is uncertain and not of proven benefit.

Supportive therapy with fluid administration, bronchodilators and physiotherapy can help.

Reference to speech and language therapists

Complications:

Without treatment, bacterial aspiration pneumonia can progress to lung abscess or bronchiectasis.

Forecast.

This depends on the underlying cause, the general well-being of the patient, the presence of complications, the speed of diagnosis and effective treatment.

Prevention.

Keep the head of the bed at a 30 ° angle: this reduces the risk or aspiration of pneumonia in people at risk.

Nasogastric feeding for patients at risk – p. Ex., Deficient jaw reflex, dysphagia.